1. Field of the Invention
The present invention relates to a manufacturing method of a hermetic container and, more particularly, to a manufacturing method of a hermetic container for an image display apparatus having electron-emitting devices in each of which an inside is held in a vacuum state and a phosphor film.
2. Description of the Related Art
Image display apparatuses of a flat panel type such as an organic LED display (OLED), a field emission display (FED), a plasma display panel (PDP), and the like are well known. Each of those image display apparatuses is equipped with a container which is manufactured by airtightly sealing glass substrates facing each other and of which an internal space is partitioned to an external space. To manufacture such a hermetic container, a spacing distance defining member, a local adhesive, and the like are arranged between the facing glass substrates as necessary, a sealing material is arranged in a frame shape to peripheral portions of the glass substrates, and a heat sealing process is executed. As a heating method of the sealing material, a method whereby the whole glass substrates are baked by a furnace and a method whereby a periphery of the sealing material is selectively heated by local heating have been known. The local heating is more advantageous than the whole heating from viewpoints of a time which is required to heat and cool, an energy which is required to heat, productivity, a prevention of thermal deformation of the hermetic container, a prevention of thermal deterioration of a function device arranged in the hermetic container, and the like. Particularly, a unit using a laser beam has been known as a unit for performing the local heating. Further, it has been known that such a manufacturing method of the hermetic container by using the local heating can be also applied as a manufacturing method of a vacuum insulated grazing glass which does not have a function device therein.
United States Patent Application Publication No. US2005/0151151 discloses a method of manufacturing a container of an OLED. In this method, a circumferential glass frit having a corner portion is first formed by using a first glass substrate as a support substrate, and the formed glass frit is flattened by weighting or controlling of application thickness by a dispenser. Then, the first glass substrate on which the flattened glass frit has been formed and a second glass substrate are disposed to face each other through the glass frit interposed therebetween, and the disposed substrates are assembled. Here, since local heating light is irradiated through scanning, a circumferential sealing material is melted, and thus the first glass substrate and the second substrate are airtightly adhered to each other.
Also, United States Patent Application Publication No. US2006/0082298 discloses a method of manufacturing a container of an OLED. In this method, a circumferential glass frit having a corner portion is first formed by using a first glass substrate as a support substrate. Then, the first glass substrate on which the glass frit has been formed and a second glass substrate are disposed to face each other through the glass frit interposed therebetween, and the disposed substrates are assembled. In such assembling, the first glass substrate and the second substrate are externally pressurized by means of a mechanical unit, whereby adherence in a sealing material region can be assured.
As just described, in order to assure the adherence between the sealing material and the glass substrate in the case where the laser beam is irradiated, a sealing method in which an assembling method has been variously improved, instead of a method of simply irradiating a laser beam to a glass substrate being a material to be bound and the sealing material, has been known.
However, there is a case where airtightness deteriorates due to a defective junction occurring at a coupling portion (corner portion) of the sealing material. That is, in general, the sealing material is provided so that plural straight line portions and coupling portions for connecting those straight line portions are formed on the glass substrate. In case of scanning the sealing material like this as irradiating the laser beam, generally, the scanning by the laser beam is performed for each of the straight line portions, and such an operation is repeated by the number of times corresponding to the number of the straight line portions. In case of adopting such a sealing method, the scanning is performed twice at about the same time to the coupling portion. The sealing material is softened and the thickness thereof decreases if the laser beam is irradiated to the sealing material, and the sealing material is hardened as it is immediately after the end of the irradiation of the laser beam. Further, when the laser beam is irradiated along the straight line, the glass substrate deforms toward the sealing material according to the decrease in the thickness of the sealing material, whereby a spacing distance between the glass substrates decreases.
When the laser beam reaches the region adjacent to the coupling portion, the thickness of the sealing material in the relevant region likewise decreases. However, since the laser beam is not yet irradiated to the coupling portion, the coupling portion still having the large thickness is connected to the plural straight line portions. For this reason, since the glass substrate in the coupling portion is bound or held by these straight line portions, the glass substrate does not easily deform toward the sealing material. As a result, in the region of the straight line portion adjacent to the coupling portion, since inconsistency occurs between the thickness of the sealing material and the spacing distance between the glass substrates, a defective junction thus occurs. The defective junction causes a decrease in joining strength and a decrease in airtightness.
The present invention is directed to the hermetic container manufacturing method which provides the sealing material between the glass substrates, and seals the glass substrates with each other by scanning the sealing material as irradiating the local heating light thereto. Here, the present invention aims to provide a manufacturing method of a high-reliability hermetic container which assures both of joining strength and airtightness.